1. Field of the Invention
This invention relates to semiconductor processing and, more particularly, to processing of III-V semiconductors.
2. Art Background
A variety of semiconductor devices based on III-V semiconductor materials are now commercially available. For example, gallium arsenide field effect transistors (GaAs FETs) are presently widely used in microwave circuitry. A series of improvements have substantially increased the performance and reliability of these devices. For example, the use of contacts to the source electrodes made through the semiconductor body of the device has been proposed as a method of improving performance. (See U.S. Pat. No. 3,986,196, issued Oct. 12, 1976.) These transistors, such as shown in FIG. 1, have a characteristic via contact, i.e., a hole through the GaAs substrate semi-insulating region, 11, buffer region 12, and active region, 13, which provides contacts to the source electrode, 14, and which engender the name via transistors. Generally, the fabrication of these III-V devices has relied on techniques, such as chemical vapor deposition, photolithography, and wet etching. Although these techniques in many instances have provided operative devices, a search is continuing for fabrication methods that either produce devices of higher quality or lead to a better production yield.